As to a handheld cleaner in the related art, a negative pressure device is generally provided inside a handle, such that the handle has a large volume and weight, which is not only inconvenient but also laborious for handholding with little comfort. In addition, as to some other handheld cleaners in the related art, although the negative pressure device is provided in a cup casing, it is encircled or surrounded by a dust collecting chamber in an entire circumference thereof, such that the negative pressure device is difficult to disassemble and maintain.